The present invention relates generally to a hermetic compressor assembly and, more particularly, to such a compressor assembly wherein pressurized gas refrigerant is directed through at least one muffling chamber prior to being discharged into the interior of the hermetically sealed housing in the vicinity of the motor windings for cooling thereof.
In general, prior art compressor assemblies of the type to which the present invention relates, comprise a housing which is hermetically sealed. Located within the housing are an electric motor and a compressor mechanism. The electric motor is connected to a crankshaft which has an eccentric portion thereon. In the case of a scotch yoke reciprocating piston compressor, the eccentric portion of the crankshaft is located within a suction cavity defined by a crankcase. Low pressure suction gas is delivered directly to the suction cavity and is compressed in radially disposed cylinders by means of piston valve assemblies reciprocably disposed therein. Gas refrigerant compressed within the cylinder is discharged through discharge ports and valves associated with a valve plate mounted to the outside of the crankcase to close off the cylinders. The discharge gas then typically enters a cylinder head cover mounted on top of the valve plate and defining a discharge space therein. From the discharge space defined by the valve plate and the cylinder head cover, the gas is routed through a muffling system to reduce noise pulsations produced by the reciprocating nature of the compressor and associated valving.
In prior art hermetically sealed scotch yoke compressor assemblies, the interior of the housing is typically at low suction pressure and, therefore, pressurized discharge gas exiting the cylinder head cover is directed through a muffler and then discharged outside of the housing. In such a configuration, a discharge muffler may take the form of a multi-piece annular muffler assembly mounted to, but not integral with, the compressor crankcase. A disadvantage of such a system is not only the complexity associated with assembling such a structure but also the need for interconnecting tubing from the cylinder head cover to the muffler and from the muffler to the exterior of the housing.
Another prior art design for a discharge muffler in a multi-cylinder scotch yoke compressor is the provision of a generally annular cavity in the bottom surface of the crankcase adjacent the oil sump and opposite the drive motor. A cover for the cavity in this design takes the form of a structure incorporating a crankshaft bearing and an oil pump. This particular prior art discharge muffler system further requires that discharge tubing connect into the annular cavity and communicate with the exterior of the housing.
Disadvantages of the aforementioned prior art muffling systems include the lack of provision for a two-stage muffler for a scotch yoke reciprocating piston compressor. Furthermore, the prior art systems are not entirely applicable to a compressor assembly having a pressurized housing into which discharge gas is released. More specifically, none of the prior art discharge muffler systems provides for effective cooling of the motor windings adjacent the compressor crankcase.